"For years, ecologists debated whether cascading effects occurred in terrestrial environments, and even then, most studies centered around the activities of top carnivores, such as wolves," Pringle said. "While top predators are undeniably important to ecological function, this new study shows that large herbivores can also play critical roles."
Extinctions, past and present
The PNAS study is timely for several reasons, he added: "Large herbivorous mammals are declining throughout Africa and worldwide, and have already gone extinct in many places. Our results suggest that these declines are likely to have complicated, and often unanticipated, consequences for the entire ecosystem."
North America is one place where mammoths, giant sloths, camels and other large herbivores once were common. But most of these mega-fauna species were eliminated during the Pleistocene epoch that ended about 10,000 years ago, raising questions about how these extinctions affected ecological processes. According to the authors, the cascading effects demonstrated in the experiment may have been important "in the history and evolution of ecosystems that today are bereft of large herbivores, and that although many of these cascades went extinct at the end of the Pleistocene along with the large herbivores that caused them, their legacies may well remain."
In 2005, another team of scientists made headlines by advocating a program of "Pleistocene re-wilding"-introducing large mammals from Africa and elsewhere into North America to simulate the lost Pleistocene fauna. Pringle made clear that his team's results do not speak to the wisdom of re-wilding. Nevertheless, he said, the new study should serve as a reminder that "the ecology we observe today is a product of history," and that hu
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
16-Jan-2007